Mark Kirkwood wrote:
The test is SELECT 1 FROM table
That should read "The test is SELECT count(1) FROM table"
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TIP 6: explain analyze is your friend
Yeah, it's pretty much a known issue for postgres
Dave
On 20-Nov-05, at 4:46 PM, Craig A. James wrote:
This article on ZDNet claims that hyperthreading can *hurt*
performance, due to contention in the L1/L2 cache by a second process:
http://news.zdnet.co.uk/0,39020330,39237341,00.htm
Has
Alan Stange wrote:
Another data point.
We had some down time on our system today to complete some maintenance
work. It took the opportunity to rebuild the 700GB file system using
XFS instead of Reiser.
One iostat output for 30 seconds is
avg-cpu: %user %nice%sys %iowait %idle
This article on ZDNet claims that hyperthreading can *hurt* performance, due to
contention in the L1/L2 cache by a second process:
http://news.zdnet.co.uk/0,39020330,39237341,00.htm
Has anyone tested this on Postgres yet? (And based on a recent somewhat
caustic thread about performance on t
Greg Stark wrote:
Alan Stange <[EMAIL PROTECTED]> writes:
Iowait is time spent waiting on blocking io calls. As another poster
pointed out, you have a two CPU system, and during your scan, as predicted,
one CPU went 100% busy on the seq scan. During iowait periods, the CPU can
be context s
On Sun, Nov 20, 2005 at 09:22:41AM -0500, Greg Stark wrote:
> I don't think that's true. If the syscall was preemptable then it wouldn't
> show up under "iowait", but rather "idle". The time spent in iowait is time in
> uninterruptable sleeps where no other process can be scheduled.
You are confus
Alan Stange <[EMAIL PROTECTED]> writes:
> > Iowait is time spent waiting on blocking io calls. As another poster
> > pointed out, you have a two CPU system, and during your scan, as predicted,
> > one CPU went 100% busy on the seq scan. During iowait periods, the CPU can
> > be context switched
William Yu wrote:
Alan Stange wrote:
Luke Lonergan wrote:
The "aka iowait" is the problem here - iowait is not idle (otherwise it
would be in the "idle" column).
Iowait is time spent waiting on blocking io calls. As another poster
pointed out, you have a two CPU system, and during your scan,
On Sat, Nov 19, 2005 at 08:13:09AM -0800, Luke Lonergan wrote:
> Iowait is time spent waiting on blocking io calls.
To be picky, iowait is time spent in the idle task while the I/O queue is not
empty. It does not matter if the I/O is blocking or not (from userspace's
point of view), and if the I/
Alan Stange wrote:
Luke Lonergan wrote:
The "aka iowait" is the problem here - iowait is not idle (otherwise it
would be in the "idle" column).
Iowait is time spent waiting on blocking io calls. As another poster
pointed out, you have a two CPU system, and during your scan, as
iowait time i
Mark Kirkwood wrote:
- I am happy that seqscan is cpu bound after ~110M/s (It's cpu bound on
my old P3 system even earlier than that)
Ahem - after reading Alan's postings I am not so sure, ISTM that there
is some more investigation required here too :-).
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